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What data structures are there in java

The data structures in Java include: Enumeration, BitSet, Vector, Stack, Dictionary, Hashtable, Properties, etc.

Jan 14, 2020 pm 01:58 PM

java data structure

Can abstract classes in java be inherited?

Abstract classes in java can be inherited. An abstract class is just a special class, but it also has the characteristics of a class. If there are abstract methods in this class, then this class must be defined as an abstract class.

Jan 14, 2020 pm 01:45 PM

java abstract class

Can map in java be sorted based on key?

Maps in java can be sorted according to key. There are two commonly used sorting methods for maps in Java, namely sort by key and sort by value.

Jan 14, 2020 pm 01:32 PM

java map

Java determines whether the socket is connected

In java, you can use the sendUrgentData method in the socket class to determine whether the socket is connected. If the SO_OOBINLINE attribute of the socket is not turned on, an exception will be thrown in java.

Jan 14, 2020 pm 01:21 PM

java

What to do if java files are written with garbled characters

Java method to avoid writing garbled files into files: Use the OutputStreamWriter() method to write files. In OutputStreamWriter, you can complete reading and writing gbk files by specifying the encoding method.

Jan 13, 2020 pm 04:35 PM

java Garbled characters

Solution to java parameter garbled problem

Solution to the problem of garbled java parameters: 1. Use the request.setCharacterEncoding() method to specify the encoding used when obtaining parameters in the post method. 2. Manually specify the parameter encoding when submitting data using the get method.

Jan 13, 2020 pm 04:11 PM

java Garbled characters

How to determine whether a string is empty or null in java

The method to determine whether a string is empty or null in Java is: 1. Use the [if(str.length() == 0)] or [if(str.equals(" "))] method to determine whether the string is empty. ;2. Use the [if(str == null)] method to determine whether the string is null.

Jan 13, 2020 am 10:49 AM

java null judgment string

How to determine whether Chinese characters are garbled in Java

How to determine whether Chinese garbled characters are garbled in Java: We can use the regular expression "\\s*|t*|r*|n*" to match the garbled characters in the string, and then determine whether it is by judging the length of the string that meets the matching rules. There are garbled characters.

Jan 09, 2020 am 10:34 AM

java Garbled characters

How to generate java project into jar file

How to generate a java project into a jar file in java: 1. The eclipse tool generates a jar file, select your project, right-click to export, and export the project as a jar file. 2. Convert java files to jar files through the jar command.

Jan 09, 2020 am 09:48 AM

java

What is the principle of polymorphism in java

The principle of polymorphism in Java is: the invocation of object methods in Java is implemented by relying on the method table in the class information. When a method of an object is called, the JVM searches the method table of the object class to determine the direct reference address of the method. , the method is actually called only after having the address.

Jan 02, 2020 am 10:12 AM

java principle Polymorphism accomplish

How to determine whether strings are equal in java

How to determine whether strings are equal in Java: 1. Use [==] to determine, but you need to pay attention to the situations of [String a = "abc"] and [String a = new String("abc")]; 2. Use [equals] method to judge.

Jan 02, 2020 am 09:35 AM

java judgment string

How to determine whether a string exists in a list collection in java

The way to determine whether a string exists in a list collection in Java is: you can use the contains method, which returns true if it exists, otherwise it returns false, for example [boolean bool = list.contains("12")].

Dec 31, 2019 pm 04:59 PM

java judgment string exist

How to package java program into jar file

The method to package a java program into a jar file is: 1. First select the project, right-click, and select [export]; 2. Then select [jar file] and select the project to be packaged; 3. Then select the path to save the jar file package , click [finish] to complete packaging.

Dec 31, 2019 pm 04:51 PM

jar file java program Pack

The difference between references in java and pointers in c++

The difference between references in Java and pointers in C++ is: 1. References have no entity when declared and do not occupy space, while pointers are assigned values ??only after they are used, and memory is not allocated when not used; 2. References The initial value is the java keyword null, and the pointer is int.

Dec 31, 2019 pm 04:38 PM

c++ java the difference Quote pointer